The present invention relates to a fuel economy indicator for a motor vehicle having an internal combustion engine, and particularly to an electronic device for providing an indication when the operating conditions of the internal combustion engine are such that the fuel consumption exceeds a predetermined threshold.
It is known that the fuel consumption of a motor vehicle having an internal combustion engine depends essentially on the speed of revolution of the engine, that is to say there is a range of engine speeds within which the fuel consumption diminishes notably if the engine is restricted to remain within this range in the various gears.
Fuel consumption indicators as such are already known. One known system operates to detect the induction air pressure, the engine operating temperature, the number of revolutions of the engine and the gear selected, and on the basis of the values of all these to signal to the driver the necessity, if the fuel consumption is to be limited, to change to a higher gear or to reduce speed. Such very complex devices are, however, very expensive, and cannot therefore be incorporated in mass produced motor vehicles intended for ordinary use.
There are, of course, some systems which are much simpler, for example if the motor vehicle has a revolution counter this may be provided with indicia which indicate the region within which it is necessary to restrict the engine speed by, for example, changing to a higher gear, in order to save fuel. Although such devices may work in theory, they are almost useless in practice since they require the frequent attention of the driver which detracts from his concentration on driving and thus increases the risk of accidents.